1. Field of the Invention
The present invention relates to a pump and more particularly a pump for liquid cosmetic substances of the cream type.
2. Related Art
Conventional pumps comprise a cylindro-conical body defining a metering chamber closed at its bottom portion by an inlet valve and at its top portion by a moving piston co-operating with resilient return means while being carried axially by a nozzle tube having a top end that projects outside the pump body and having a bottom end that is provided with at least one delivery orifice.
Such pumps are designed to be fitted to containers such as bottles and the assembly as a whole thus forms a packaging and dispensing system.
Such pumps are described in particular in EP 0 888 824 and EP 0 757 004 in which the piston is also slidably mounted firstly about the nozzle tube between a closure position closing the delivery orifice and an open position in which said orifice is fully open, and secondly in sealed peripheral contact with the inside wall of said chamber between a top end-of-stroke abutment and a bottom end-of-stroke abutment; the coefficient of friction between the piston and the tube being less than the coefficient of friction between said piston and the inside wall of the body.
However, certain cosmetic substances have a naturally tendency to dry out when exposed to air. Consequently, any substance that has not been expelled and that remains in the nozzle tube between two uses is capable of creating an artificial plug which can subsequently hinder or prevent the substance from being dispensed.
An object of the present invention is to resolve this technical problem in satisfactory manner.
The invention achieves this object by means of a pump of the above-mentioned type characterized in that the bottom end-of-stroke abutment of the piston in the chamber is formed by ribs that extend along the wall of said chamber parallel to the generator lines of said body, and in that said piston is constituted by a central sleeve that surrounds the nozzle tube, having an inside wall that has a top recess defining an annular bottom, and that is extended radially outwards by a peripheral ring via a connecting spacer, the stroke of the piston over the tube being upwardly limited by abutment of the bottom of said recess against the bottom circumference of a projection of complementary profile secured to said tube.
According to an advantageous characteristic, the stroke of the piston over the nozzle tube is determined in such a manner that, when the tube rises, a volume of substance corresponding to the residue contained in said tube is sucked back into the chamber.
According to another characteristic, the resilient return means act on the bottom end of the nozzle tube which extends inside the metering chamber.
In a specific embodiment, the top abutment of the piston is formed by the bottom inside edge of a collar covering the top portion of the body and ensuring that the nozzle tube is held.
In yet another embodiment, the closure position of the delivery orifice corresponds to the piston being in contact with the projecting annular rim of a tip fitted over at least part of the bottom end of said tube beneath the level of said orifice and receiving thrust from the return means.
In a variant, the projecting rim has a tapering inside profile co-operating with the beveled bottom edge of the piston so as to ensure that the delivery orifice is closed in sealed manner.
The pump of the invention enables the nozzle tube to be cleared automatically of any substance after each delivery.
Thus, all the components of the dispensing head (nozzle tube, pushbutton, nozzle, . . . ) are always cleaned and all of the substance is contained in spaces that are closed and isolated from the outside.
The pump of the invention therefore ensures sealed and protective confinement for the substance, thereby preserving its quality and its intrinsic properties.